Bun 2.0 is surprisingly production-ready

The migration

A 12-route Express-style API with pg, redis, and a few heavy dependencies. Migration took 4 hours, most of which was dealing with native addons.

What improved

• Cold start: 340ms (Node) → 38ms (Bun)
• npm install: 18s → 4s
• Test suite: 22s → 7s

What broke

• --experimental-vm-modules Jest tests need rewriting for Bun's test runner
• One native module (argon2) required a rebuild
• Some require / import interop edge cases in old code

Verdict

For greenfield services: use Bun now. For migrations: plan a half-day per service, budget time for native addon issues.